DESCRIPTION: In mammals, energy homeostasis requires the carefully timed orchestration of numerous metabolic processes. An endogenous circadian timing system ensures that metabolic enzymes are produced at just the right time within the day-night cycle to match the organism's food availability and fuel needs. Lipid, carbohydrate and glucose balance, as well as the secretion of hormones are all recognized to be under circadian control. Altering the sleep-wake cycles in humans causes metabolic disturbances, including reduced insulin sensitivity and glucose intolerance. In peripheral tissues and organs, the timing of gene expression involves transcription factors including the core clock components and the nuclear receptors Rev-Erb? and Rev-Erb. The Rev-Erbs directly regulate the expression of many of the core clock components, but also act as master transcriptional regulators of lipid balance, adipogenesis, and glucose output. Similar to other nuclear receptors, the Rev-Erbs contain an internal hydrophobic cavity within their ligand binding domains (LBDs) that can be exploited for drug discovery. We previously identified heme as the endogenous ligand for the Rev-Erbs, and showed that reversible heme binding regulates their transcriptional activities. More recently, a single molecular class of Rev-Erb?/ modulators was developed and shown to significantly alter the lipid and glucose gene programs in animals. Diet-induced obese animals treated with Rev-Erb modulators display remarkably reduced fat mass and improvements in their lipid and cholesterol profiles and plasma glucose levels. We now seek to identify many new classes of Rev-Erb binding molecules, including modulators that act specifically on each of the Rev- Erb? and Rev-Erb receptors. To find such modulators, we have developed and optimized a novel high- throughput assay that efficiently identifies molecules that bind within the LBDs, or within the domain-domain junctions of their quaternary structures. We propose to carry out a pair of high-throughput screening campaigns using the MLPCN library and a battery of secondary/confirmatory assays and gene expression studies that identify the most promising Rev-Erb?/ modulators. The overall goal is to find and develop molecules with potential benefits for obesity, diabetes, and hyperlipidemia.